1. Field of the Invention
The present invention relates generally to a magnetic disk apparatus and, more particularly, to a magnetic disk apparatus of the servo control type which employs as a servo head one of a plurality of heads which cooperate with a disk assembly having a plurality of magnetic disks.
2. Description of the Prior Art
In the field of magnetic disk apparatus used as, for example, one type of external storage devices for general-purpose electronic computers, there has recently been a demand for increases in storage capacity and operating speed. To meet this demand, a magnetic disk apparatus has been developed of the type which is provided with a multiplicity of magnetic disks serving as a storage medium and a multiplicity of heads for effecting recording and reproduction of information on and from the respective magnetic disks. One example of this type of magnetic disk apparatus is disclosed in U.S. Pat. No. 4,714,972.
In such a magnetic disk apparatus as is provided with a multiplicity of magnetic disks, in order to facilitate production and assembly of individual parts, it is common practice to employ head supporting structures all of which have the same structures. The head supporting structures are for connecting heads to an actuator for positioning the respective heads at desired positions on the corresponding disks, and, each constituted by a head arm, a leaf spring and a core slider for floating the head from the corresponding magnetic disk.
In such a situation, a servo control system is proposed as one example of a control system for controlling seek operation, that is, the operation of positioning a plurality of heads on corresponding magnetic disks by means of an actuator. In the known servo control system, one disk selected from a plurality of the magnetic disks is used as a servo disk, while one head selected from a plurality of the heads is used as a servo head. Servo information is recorded in advance on the servo disk. The servo information is read from the servo disk by the servo head and fed back for use in control of the actuator, whereby positioning of the data heads on the corresponding magnetic disks is controlled.
However, the above-described conventional type of magnetic disk apparatus involves a problem that, since the servo head and the data head for effecting normal recording and reproduction of information are respectively secured to the actuator by head supporting structures having the same structures, all the head supporting structures have the same proper oscillation. As a result, when high-speed seek operations are repeated, each data head vibrates and the vibration is inevitably transmitted to the servo head due to the resonance phenomenon of the head supporting structures. This leads to a fall in the positioning accuracy of each head during seek operation.
The above-described problem is serious when the speed of seek operation is to be increased to shorten the access time in order to achieve an even higher operating speed of the magnetic disk apparatus.